SLAA547C July   2013  – July 2021 MSP430FR5739

 

  1. 1Software Benchmarks
    1. 1.1 AES Benchmarks
    2. 1.2 DES Benchmarks
    3. 1.3 SHA-2 Benchmarks
  2. 2Using Library Functions
    1. 2.1 AES 128
      1. 2.1.1 Encrypting With AES 128
      2. 2.1.2 Decrypting With AES 128
    2. 2.2 DES
      1. 2.2.1 Setting the Key Schedule for DES
      2. 2.2.2 Encrypting and Decryption With DES
      3. 2.2.3 Encryption and Decryption With DES CBC Mode
    3. 2.3 3DES
      1. 2.3.1 Encrypting and Decrypting With Triple DES
    4. 2.4 SHA-2
      1. 2.4.1 Hashing With SHA-256
      2. 2.4.2 Hashing With SHA-224
  3. 3Overview of Library Functions
    1. 3.1 AES 128
      1.      aes_enc_dec
      2.      aes_encrypt
    2. 3.2 DES and 3DES
      1.      Des_Key
      2.      Des_Enc
      3.      Des_Dec
      4.      DES_ENC_CBC
      5.      DES_DEC_CBC
      6.      TripleDES_ENC
      7.      TripleDES_DEC
      8.      TripleDES_ENC_CBC
      9.      TripleDES_DEC_CBC
    3. 3.3 SHA-256 and SHA-224
      1.      SHA_256
  4. 4Cryptographic Standard Definitions
    1. 4.1 AES
      1. 4.1.1 Basic Concept of Algorithm
      2. 4.1.2 Structure of Key and Input Data
      3. 4.1.3 Substitute Bytes (Subbytes Operation)
      4. 4.1.4 Shift Rows (Shiftrows Operation)
      5. 4.1.5 Mix Columns (Mixcolumns Operation)
      6. 4.1.6 Add Round Key (Addroundkey Operation)
      7. 4.1.7 Key Expansion (Keyexpansion Operation)
    2. 4.2 DES and 3DES
      1. 4.2.1 DES Algorithm Structure
      2. 4.2.2 The Function Block
      3. 4.2.3 Key Schedule
      4. 4.2.4 Triple DES
      5. 4.2.5 Cipher Block Chaining (CBC) Mode
    3. 4.3 SHA-256 and SHA-224
      1. 4.3.1 Message Padding and Parsing
      2. 4.3.2 SHA-256 Algorithm
      3. 4.3.3 Equations Found in SHA-256 Algorithm
      4. 4.3.4 SHA-224
  5. 5References
    1.     Revision History

4.1.5 Mix Columns (Mixcolumns Operation)

Probably the most complex operation from a software implementation perspective is the Mixcolumns step. The working method of Mixcolumns can be seen in Figure 4-5.

GUID-6D06CE42-CAAF-4F46-AD13-4C0354970F0B-low.gifFigure 4-5 Mixcolumns Operation

Opposed to the Shiftrows operation, which works on rows in the 4x4 state matrix, the Mixcolumns operation processes columns.

In principle, only a matrix multiplication needs to be executed. To make this operation reversible, the usual addition and multiplication are not used. In AES, Galois field operations are used. This document does not go into the mathematical details, it is only important to know that in a Galois field, an addition corresponds to an XOR and a multiplication to a more complex equivalent.

The fact that there are many instances of 01 in the multiplication matrix of the Mixcolumns operation makes this step easily computable.